Add alphaType() to SkImage

src/image/SkImage_Generator.cpp

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkImage_Base.h"
 #include "SkBitmap.h"
 #include "SkCanvas.h"
 #include "SkData.h"
 #include "SkImageCacherator.h"
 #include "SkImagePriv.h"
 #include "SkPixelRef.h"
 #include "SkSurface.h"
 
 class SkImage_Generator : public SkImage_Base {
 public:
     SkImage_Generator(SkImageCacherator* cache)
         : INHERITED(cache->info().width(), cache->info().height(), cache->uniqueID())
         , fCache(cache) // take ownership
     {}
 
     virtual SkImageInfo onImageInfo() const override {
         return fCache->info();
     }
+    SkAlphaType onAlphaType() const override {
+        return fCache->info().alphaType();
+    }
 
     bool onReadPixels(const SkImageInfo&, void*, size_t, int srcX, int srcY, CachingHint) const override;
     SkImageCacherator* peekCacherator() const override { return fCache; }
     SkData* onRefEncoded(GrContext*) const override;
-    bool isOpaque() const override { return fCache->info().isOpaque(); }
     sk_sp<SkImage> onMakeSubset(const SkIRect&) const override;
     bool getROPixels(SkBitmap*, CachingHint) const override;
     GrTexture* asTextureRef(GrContext*, const GrTextureParams&,
                             SkSourceGammaTreatment) const override;
     bool onIsLazyGenerated() const override { return true; }
 
 private:
     SkAutoTDelete<SkImageCacherator> fCache;
 
     typedef SkImage_Base INHERITED;
@@ skipping 35 matching lines @@
 GrTexture* SkImage_Generator::asTextureRef(GrContext* ctx, const GrTextureParams& params,
                                            SkSourceGammaTreatment gammaTreatment) const {
     return fCache->lockAsTexture(ctx, params, gammaTreatment, this);
 }
 
 sk_sp<SkImage> SkImage_Generator::onMakeSubset(const SkIRect& subset) const {
     // TODO: make this lazy, by wrapping the subset inside a new generator or something
     // For now, we do effectively what we did before, make it a raster
 
     const SkImageInfo info = SkImageInfo::MakeN32(subset.width(), subset.height(),
-                                      this->isOpaque() ? kOpaque_SkAlphaType : kPremul_SkAlphaType);
+                                                  this->alphaType());
     auto surface(SkSurface::MakeRaster(info));
     if (!surface) {
         return nullptr;
     }
     surface->getCanvas()->clear(0);
     surface->getCanvas()->drawImage(this, SkIntToScalar(-subset.x()), SkIntToScalar(-subset.y()),
                                     nullptr);
     return surface->makeImageSnapshot();
 }
 
 sk_sp<SkImage> SkImage::MakeFromGenerator(SkImageGenerator* generator, const SkIRect* subset) {
     if (!generator) {
         return nullptr;
     }
     SkImageCacherator* cache = SkImageCacherator::NewFromGenerator(generator, subset);
     if (!cache) {
         return nullptr;
     }
     return sk_make_sp<SkImage_Generator>(cache);
 }